- New payYear() controller action: processes all unpaid subscriptions for a
  member's financial year in one transaction with a single receipt
- Route: POST /members/{memberId}/subscriptions/{year}/pay
- View: replaced per-row pay buttons with a single "سداد اشتراك بالكامل" button
  at the bottom of each year section showing total due
- Itemized table remains for transparency (shows each person's breakdown)
- Added discount_amount column to the table display
- FIFO still enforced: only oldest unpaid year's button is active
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>